Two weeks ago, I took several vacation days to play in my garden. For the better part of four days, I planted bulbs, divided perennials and started my fall cleanup.
Luckily, the days were the best mid-October could offer, with temperatures in the 70s and 80s. Bright blue skies were accented by gently falling leaves — leaves so light and easy to rake into my beds because of the dry weather.
Fast forward to early November, when wind and rain from Superstorm Sandy cleared most of the leaves from trees, leaves that now rest in heavy clumps in lawns and landscape beds. Although many gardeners got a jump on leaf cleanup before Sandy hit, others will face the cleanup of wet leaves in the cooler days of November.
But before you bag and throw out all those leaves, reconsider them as a benefit to the garden instead of a waste product. Leaves have many garden uses, whether they’re shredded into the lawn, composted or used whole or shredded in bed areas as mulch.
One of the first objections held up against leaves involves soil pH: Don’t leaves alter pH, making the soil too acid for garden plants?
As leaves break down, the fear is they may contribute to a decrease in pH (which equals increased acidity). This may be a concern over time when mulching with pine needles on sandy soils, but is generally not a problem in our area, since we don’t tend to have ample supplies of pine needles for mulch, or sandy soils.
Additionally, our soils have a high buffering capacity, meaning that despite attempts to lower the pH, the soil tends to return over time to the same pH level. Soil pH can be easily monitored by testing every three years, and lime can be added as needed to adjust to an ideal pH.
Another objection to leaves is that they can become matted when wet, and can restrict air and water flow in soils. This can be a concern if whole leaves are left on lawn areas for extended periods of time. For this reason, leaves should be mowed and shredded on the lawn. If they are shredded several times throughout the fall, the leaf clippings will work their way onto the soil surface and are unlikely to smother the grass.
Research has shown that lawns can absorb many pounds of shredded leaves with no detrimental effects. One Purdue study involved mowing 4,000 pounds of leaves per acre into turf grass each year over a five-year period. Results showed no increase in disease or weed problems, no pH or nutrient availability issues, and an increase in microbial activity associated with improved soil quality.
Leaves are a positive addition to soils: They add needed organic matter, which in turn improves soil structure, nutrient availability and water-holding capacity. Leaves also provide micronutrients, which are elements needed by plants in small quantities. Most commercial fertilizers do not provide micronutrients, such as zinc, iron and manganese; leaves can be an important source of these nutrients.
The benefits of leaf amendments can be clearly seen at the gardens of the Kingwood Center in Mansfield, where leaves have been added into the planting beds for close to thirty years. Senior gardener Charles Applegate describes Kingwood’s soil as chocolate cake — it’s hard to think of a more accurate description. The dark, fluffy soil at Kingwood is a gardener’s dream. It’s so loose it looks as though you could use your bare hands to dig and plant.
Leaves are composted at Kingwood and used as a twice-a-year amendment to create a rich, highly organic soil. The leaf mulch also does an excellent job of preventing weed problems.
Think twice, then, before you send your free soil amendment out with the garbage. By recycling leaves into the lawn and into garden beds, you’ll improve soil conditions for your plants, as well as save money and natural resources that would otherwise be used to remove and then replace that important source of organic matter. Instead of cursing the falling leaves, think of them as a free source of fertilizer, compost and mulch.
Denise Ellsworth directs the honeybee and native pollinator education program for Ohio State University. If you have questions about caring for your garden, contact her at 330-263-3700 or click on the Ask Denise link on her blog at www.osugarden.com.